Extreme scenario-based risk assessment of landslide-induced impulse wave from spoil disposal slope instability in hy-dropower projects

In the development of hydropower projects in high-mountain gorge regions, the insta-bility of high-position spoil disposal areas under extreme scenarios and the subsequent disaster chains triggered by landslide-induced impulse waves pose serious threats to watershed safety. However, existing risk assessment approaches often separate geo-mechanical stability analysis from hydrodynamic simulations, thereby lacking an in-tegrated perspective on the dynamic processes from slope failure to wave propagation. This study focuses on the Riganggou spoil disposal area in the Yalong River Basin and employs a fully coupled analytical framework combining finite difference and compu-tational fluid dynamics methods to simulate the evolution of slope stability and im-pulse wave dynamics. Results demonstrate that under combined extreme rainfall and seismic conditions, the spoil slope approaches a critical state of instability, with a safe-ty factor of 1.005. The resulting impulse waves, strongly influenced by river channel topography, exhibit nonlinear propagation behavior characterized by high-energy concentrations in the near field and rapid attenuation in the far field. Risk assessment reveals that although dam structures and downstream residential areas remain within safe limits, riverside highways are susceptible to partial inundation and wave impact. By proposing a coupled framework for stability evolution and impulse wave risk eval-uation, this study offers a practical technical pathway for disaster chain risk mitiga-tion in large-scale watershed engineering.